Disk Tasks

The following disk tasks are supported:

Changing the Default Disk Format Setting

When disks are put under VxVM control, they are formatted with the default cdsdisk layout. This happens during the following operations:

Initialization of disks
Encapsulation of disks with existing partitions or slices (Linux and Solaris systems)
Conversion of LVM disks (AIX, HP-UX and Linux systems)

You can override this behavior by changing the settings in the system defaults files as described in Defaults Files. For example, you can change the default format to sliced for disk initialization by modifying the definition of the format attribute in the /etc/default/vxdisk defaults file. To change the default format for disk encapsulation or LVM disk conversion, change the definition of the format attribute in the /etc/default/vxencap defaults file.

Restoring CDS Disk Labels

CDS disks have three labels:

Platform block
AIX coexistence label
HP coexistence/VxVM ID block

There are also backup copies of each. If any of the primary labels become corrupted, VxVM will not bring the disk online and user intervention is required.

If two of the three labels are intact, the disk is still recognized as a cdsdisk (though in the 'error' state) and vxdisk flush can be used to restore the CDS disk labels from their backup copies.

Primary labels are at sectors 0, 7, and 16; and a normal flush will not flush sectors 7 and 16. Also, the private area is not updated as the disk is not in a disk group. There is no means of finding a "good" private region to flush from. In this case, it is possible to restore the CDS disk labels from the existing backups on disk using the flush operation.

If a corruption happened after the labels were read and the disk is still online and part of a disk group, then a flush operation will also flush the private region.

Caution Caution and knowledge must be employed because the damage could involve more than the CDS disk labels. If the damage is constrained to the first 128K (as would be the case if some entity on the fabric - such as a Windows box - wrote a disk label to a disk which was actually a cdsdisk being used in some disk group), then the disk flush would fix it.

Use the following command to rewrite the CDS ID information to a specific disk (this rewrites all labels except sectors 7 and 16):

# vxdisk flush disk_accessname

Use the following command to rewrite all the disks in a CDS disk group (this rewrites all labels except sectors 7 and 16):

# vxdg flush dg_name

Use the -f option with the vxdisk command to forcibly rewrite the AIX coexistence label (sector 7), VxVM ID block (sector 16), and HP-UX Coexistence Labels:

# vxdisk -f flush disk_accessname

This command rewrites all labels if there exists a valid VxVM ID block that points to a valid private region.

Note Sectors 7 and 16 are only rewritten if the -f flag is given. The reason for this is that these sectors lay within the first track of the disk, and Windows systems use the first track for their own purposes. In the example above where the disk was taken offline due to label corruption, if it involved sectors 7 or 16, then -f is required to fix the problem.


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Product: Storage Foundation Guides
Manual: Storage Foundation 4.1 Cross-Platform Data Sharing Administrator's Guide
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